SN 6.1 Ayacana Sutta
I have heard that on one occasion, when the Blessed One was newly Self-awakened, he was staying at Uruvela on the bank of the Nerañjara River, at the foot of the Goatherd's Banyan Tree. Then, while he was alone and in seclusion, this line of thinking arose in his awareness: "This Dhamma that I have attained is deep, hard to see, hard to realize, peaceful, refined, beyond the scope of conjecture, subtle, to-be-experienced by the wise. But this generation delights in attachment, is excited by attachment, enjoys attachment. For a generation delighting in attachment, excited by attachment, enjoying attachment, this/that conditionality and dependent co-arising are hard to see. This state, too, is hard to see: the resolution of all fabrications, the relinquishment of all acquisitions, the ending of craving; dispassion; cessation; Unbinding. And if I were to teach the Dhamma and if others would not understand me, that would be tiresome for me, troublesome for me."
Enough now with teaching
only with difficulty
This Dhamma is not easily realized
by those overcome
with aversion & passion.
What is abstruse, subtle,
hard to see,
going against the flow —
those delighting in passion,
cloaked in the mass of darkness,
As the Blessed One reflected thus, his mind inclined to dwelling at ease, not to teaching the Dhamma.
Then Brahma Sahampati, having known with his own awareness the line of thinking in the Blessed One's awareness, thought: "The world is lost! The world is destroyed! The mind of the Tathagata, the Arahant, the Rightly Self-awakened One inclines to dwelling at ease, not to teaching the Dhamma!" Then, just as a strong man might extend his flexed arm or flex his extended arm, Brahma Sahampati disappeared from the Brahma-world and reappeared in front of the Blessed One. Arranging his upper robe over one shoulder, he knelt down with his right knee on the ground, saluted the Blessed One with his hands before his heart, and said to him: "Lord, let the Blessed One teach the Dhamma! Let the One-Well-Gone teach the Dhamma! There are beings with little dust in their eyes who are falling away because they do not hear the Dhamma. There will be those who will understand the Dhamma."
That is what Brahma Sahampati said. Having said that, he further said this:
In the past
there appeared among the Magadhans
an impure Dhamma
devised by the stained.
Throw open the door to the Deathless!
Let them hear the Dhamma
realized by the Stainless One!
Just as one standing on a rocky crag
might see people
all around below,
So, O wise one, with all-around vision,
ascend the palace
fashioned of the Dhamma.
Free from sorrow, behold the people
submerged in sorrow,
oppressed by birth & aging.
Rise up, hero, victor in battle!
O Teacher, wander without debt in the world.
Teach the Dhamma, O Blessed One:
There will be those who will understand.
Then the Blessed One, having understood Brahma's invitation, out of compassion for beings, surveyed the world with the eye of an Awakened One. As he did so, he saw beings with little dust in their eyes and those with much, those with keen faculties and those with dull, those with good attributes and those with bad, those easy to teach and those hard, some of them seeing disgrace and danger in the other world. Just as in a pond of blue or red or white lotuses, some lotuses — born and growing in the water — might flourish while immersed in the water, without rising up from the water; some might stand at an even level with the water; while some might rise up from the water and stand without being smeared by the water — so too, surveying the world with the eye of an Awakened One, the Blessed One saw beings with little dust in their eyes and those with much, those with keen faculties and those with dull, those with good attributes and those with bad, those easy to teach and those hard, some of them seeing disgrace and danger in the other world.
Having seen this, he answered Brahma Sahampati in verse:
Open are the doors to the Deathless
to those with ears.
Let them show their conviction.
Perceiving trouble, O Brahma,
I did not tell people the refined,
Then Brahma Sahampati, thinking, "The Blessed One has given his consent to teach the Dhamma," bowed down to the Blessed One and, circling him on the right, disappeared right there.